CN102375352B - Environmental compensation alignment system - Google Patents

Abstract

The invention relates to an alignment system adopted for lithography equipment. The alignment system comprises a light source and lighting module, an alignment mark, an imaging module, a reference grating, a signal acquisition and processing module, a workpiece table, a movement station, a position acquisition and movement control module, an environmental measurement module and an alignment operation and management module. According to the present invention, the environmental measurement module is adopted to real-timely measure parameters of the alignment beam propagation environment, and the parameters are adopted to compensate the alignment error caused by environmental fluctuation during the alignment process so as to improve the alignment accuracy and the measurement stability.

Description

A kind of ambient compensation alignment system

Technical field

The present invention relates to integrated circuit or other microdevice and make the lithographic equipment in field, relate in particular to a kind of ambient compensation alignment system for lithographic equipment.

Background technology

Lithographic equipment typically refers to the major equipment of making integrated circuit and/or other micromodule equipments.By lithographic equipment, (different documents also are translated as mask, and being exposed in the substrate of figure Hereinafter the same) is as semiconductor wafer or LCD plate to have different masks.The scope of lithographic equipment includes but not limited to: integrated circuit is made lithographic equipment, panel display board lithographic equipment, MEMS/MOEMS lithographic equipment, advanced encapsulation lithographic equipment, printed circuit board (PCB) lithographic equipment, printed circuit board (PCB) processing unit (plant) and printing circuit board element mounting device etc.

In the semiconducter IC ic manufacturing process, complete chip need just can complete through photolithographic exposure repeatedly usually.Except the photoetching first time, the photoetching of all the other levels figure that stays that all figure of this level and level in the past will be exposed before exposure is accurately located, and could guarantee like this has correct relative between each layer pattern, i.e. alignment precision.Generally, alignment precision is 1/3～1/5 of litho machine resolution index, and for the litho machine of 100 nanometers, the alignment precision index request is less than 35 nanometers.Alignment precision is one of the key technical indexes of projection mask aligner, and the alignment precision between mask and the silicon chip is the key factor that influences alignment precision.When characteristic dimension CD requires more hour, the requirement of alignment precision and the requirement of consequent alignment precision are become stricter, as CD dimensional requirement 10 nanometers or the littler alignment precision of 90 nanometers.

Between mask and the silicon chip to adopting mask registration to add the mode that silicon chip is aimed at, namely be labeled as bridge with the work stage datum plate, set up the position relation between mask mark and the silicon chip mark.The basic process of aiming at is: at first by the mask registration system, realize aiming between mask mark and the work stage datum plate mark, utilize silicon chip alignment system then, finish aiming between silicon chip mark and the work stage datum plate mark, and then realize indirectly aiming between silicon chip mark and the mask mark.

Patent US6297876B1, CN03164858.4, CN03164859.2, CN200510030577.8 etc. have introduced silicon chip (from the axle) alignment system of a class based on optical grating diffraction.This class alignment system adopts the alignment mark (as 16 microns and 17.6 microns) that comprises two different cycles sub-gratings, by survey two sub-gratings ± 1 grade of interference of light picture sees through the light intensity signal with reference to grating, through the match of signal, determine the coarse alignment position of mark; Simultaneously by surveying the senior diffraction light interference imaging (as ± 5 grades of light) of 16 microns cycle sub-gratings, and through the match of signal, at the definite fine alignment (measurement) in coarse alignment (measurements) basis.Patent CN200710045495X, CN2007100454964, CN200710044153.6, CN200710044152.1, CN200810040234.3 have announced a kind of silicon chip (from axle) alignment system of improved optical grating diffraction, on definite coarse alignment basis, this alignment system does not utilize senior diffraction light signal, but utilize meticulous sub-gratings ± 1 grade interference of light image signal, through signal fitting, determine the fine alignment position.

But, in the alignment system that adopts foregoing invention to give, owing to be not invariable to the environment in the punctual diffracted beam travel path, fluctuation as the image-forming module internal environment, environmental variance exists fluctuation (as temperature between image-forming module and the alignment mark, pressure and humidity etc.), the fluctuation of these environmental variances causes the refractive index of air to change, the wavelength of the alignment of propagating in this environment will change, its wave vector (phase changing capacity in the unit length) also will change thereupon, finally cause the interference of light at different levels to be imaged on reference to the position on the grating and be offset.And the position of aiming at is to determine that by interference imaging and with reference to the relative position between the grating this will introduce alignment error.Usually, in 30 seconds, temperature fluctuation 7.3mk, pressure surge 2.5Pa will introduce the alignment error of 0.5 nanometer.Therefore, be necessary to provide a kind of alignment system with high alignment precision and high measurement stability.

Summary of the invention

The object of the present invention is to provide a kind of new alignment system, this system can effectively solve the problem of the alignment error that environment causes in the prior art.

A kind of alignment system for lithographic equipment, this system comprises: light source and the lighting module of aiming at illuminating bundle are provided; Alignment mark is carried out the image-forming module of imaging; With reference to grating; Gather and see through with reference to the light intensity signal of grating and the signal acquisition process module of handling; Alignment mark; The work stage of carrying silicon chip; The motion platform; Gather the positional information of the work stage of carrying silicon chip, and negotiate synchronously with alignment function and administration module, planning movement locus, the station acquisition of the motion of controlled motion platform and motion-control module; Alignment function and administration module with the signal that receives signal acquisition process module and station acquisition and motion-control module is characterized in that:

Also comprise the environment measurement module, described environment measurement module is used for measuring and gathering and aim at the residing environmental variance of diffracted beam round, and the environmental variance information that collects is transferred to alignment function and administration module; Described alignment function and administration module utilize light intensity data, work stage position data and environmental variance information to determine aligned position.

The environmental variance that described environment measurement module is measured image-forming module inside changes, or measures the environmental variance variation between image-forming module and the alignment mark, or the two is all measured.

Described environmental variance is aimed at one or more in the environmental variance of refractive index of diffracted beam propagation medium for influence.

Described environmental variance is temperature, pressure and humidity.

Described alignment function and administration module utilize the light intensity data of each passage and the work stage position data that shares, and through data fitting, determine a series of peak values of each channel alignment signal.

Described alignment function and administration module utilize a series of peak values of each channel alignment signal of environmental variance information correction.

Described modification method adopts environmental variance-peak skew mathematical model to revise.

Described environmental variance-peak skew mathematical model is:

$\left\{\begin{array}{c}\mathrm{\Δ\φ}=f(\mathrm{\λ},L,P,T,...,h,P_0,T_0,...,h_0)\\ {\mathrm{\ΔX}}_i=S_i\mathrm{\Δ\φ}\\ X_{\mathrm{peak},i}^{\′}=X_{\mathrm{peak},i}+{\mathrm{\ΔX}}_i\end{array}\right.$

In the formula, f () is phase shift function, and Δ φ is phase deviation, and λ is for aiming at illumination wavelengths, and L is for aiming at diffracted beam propagates light path difference, P, T ..., h be pressure, temperature ..., each environmental variance measured value such as humidity, P ₀, T ₀..., h ₀Reference value for working environment.S _iBe the cycle of i channel alignment signal, Δ X _iBe the position deviation of this signal peak, X _{Peak, i}A series of peaks of the i channel alignment signal that obtains for match, X ' _{Peak, i}Peak for revised i channel alignment signal.

Described phase shift function is the Gladstone-Dale approximate formula:

$\mathrm{\Δ\φ}=\frac{2\mathrm{\πL}}{\mathrm{\λ}}(1+2.9155*{10}^{-8}(\frac{P}{T}-\frac{P_0}{T_0}))$

In the formula, Δ φ is phase deviation, and λ is for aiming at illumination wavelengths, and L is for aiming at diffracted beam propagates light path difference, and P, T are the measured value of pressure and temperature, P ₀, T ₀Reference value for pressure and temperature.

The mean value of each the environmental variance series of measured values when described each environmental variance measured value is alignment scanning perhaps is the measured value in the moment in the middle of the alignment scanning.

Described modification method adopts environmental variance-peak offset table to revise.

Described environmental variance-peak offset table is data or historical data foundation by experiment.

Described modification method is by tabling look-up or the method for interpolation is carried out.

Described modification method is:

$X_{\mathrm{peak},i}^{\′}=X_{\mathrm{peak},i}+\mathrm{\Δ}{\hat{X}}_i$

In the formula,

For by tabling look-up or interpolation obtains the peak deviation of the i channel alignment signal of environmental variance variable quantity correspondence, X _{Peak, i}A series of peaks of the i channel alignment signal that obtains for match, X ' _{Peak, i}Peak for revised i channel alignment signal.

Alignment system of the present invention is on the basis of prior art, increased the environment measurement module, utilize this environment measurement module to measure the parameter of alignment communication environments in real time, and by setting up the relation between environmental variance and the registration signal peak deviation, definite signal peak position deviation that punctual environmental fluctuating is caused is revised aligned position then.This alignment system can compensate the alignment error that the variation to punctual environmental variance causes effectively, thereby has improved alignment precision and measured stability.

Description of drawings

By the embodiment of the invention and in conjunction with the description of its accompanying drawing, can further understand purpose, specific structural features and the advantage of its invention.Wherein, accompanying drawing is:

Figure 1 shows that the structural representation according to alignment system of the present invention;

Figure 2 shows that peak calculations of offset synoptic diagram;

Figure 3 shows that the relation table of refractive index and peak skew.

Embodiment

Below, describe in detail according to a preferred embodiment of the invention by reference to the accompanying drawings.For convenience of description and highlight the present invention, omitted existing associated components in the prior art in the accompanying drawing, and will omit the description to these well-known components.

Figure 1 shows that the structural representation according to alignment system of the present invention.This alignment system comprises: light source and lighting module 1; Image-forming module 2; With reference to grating 3; Signal acquisition process module 4; Alignment mark 5 comprises datum plate mark and the silicon chip mark that is positioned on the silicon chip 6; Work stage 7; Motion platform 8; Station acquisition and motion-control module 9; Alignment function and administration module 10; Environment measurement module 11.Light source and lighting module 1 provide illumination beam to alignment mark 5, form the diffraction light that carries label information, and diffraction light is imaged onto with reference on grating 3 surfaces by image-forming module 2.Signal acquisition process module 4 is gathered the alignment mark imaging through the light intensity signal with reference to grating 3, and after treatment light intensity data is transferred to alignment function and administration module 10.Station acquisition and motion-control module 9 are gathered the positional information of the work stage 7 of carrying silicon chip, and negotiate planning movement locus, the motion of controlled motion platform 8 synchronously with alignment function and administration module 10.Simultaneously, station acquisition and motion-control module 9 are transferred to alignment function and administration module 10 with the position data of the work stage 7 that collects.Environment measurement module 11 is used for measuring and gathering and aim at the residing environmental variance information of diffracted beam round, and the environmental variance information that collects is transferred to alignment function and administration module 10.Alignment function and administration module 10 utilize light intensity data, work stage position and environmental variance information to determine aligned position.

Light source and lighting module 1 comprise the illuminating bundle of one or more discrete wavelength, for example, and 633 nanometers and 532 nanometers.

Alignment mark 5 comprises datum plate mark and silicon chip mark.The datum plate mark is positioned on the datum plate of work stage, and silicon chip mark is positioned on the silicon chip.In the silicon chip photoetching is produced, at first utilize the datum plate mark to aim at, aim at by this, can obtain the aligned position of datum plate mark; And then utilize silicon chip mark to aim at, and can obtain the aligned position of silicon chip mark, can obtain the position relation between silicon chip mark and the datum plate mark at last.The datum plate mark is aimed at silicon chip mark and is aligned to similar process, so in the present invention hereinafter describes, no longer distinguish datum plate mark or silicon chip mark, unified is alignment mark.

Image-forming module 2 is formed the 4f imaging system jointly by preceding group of lens and back group lens, and by the diffraction light in the unwanted level of diaphragm filtering between preceding group of lens and the back group lens time, keeps required grade of inferior diffraction light.

Station acquisition and motion-control module 9 comprise placement data acquisition unit and motion control unit, the placement data acquisition unit is used for gathering the positional information of work stage 7, and the position data of work stage 7 offered motion control unit and alignment function and administration module in real time, the motion of motion control unit controlled motion platform under alignment function and administration module management.

Signal acquisition process module 4 comprises photodetector and signals collecting and processing unit, photodetector is converted to electric signal with light signal, signals collecting and processing unit are with the electric signal that the obtains processing such as amplification, discrete sampling that gain, and the light intensity data after will handling is transferred to alignment function and administration module 10.

All cause the environmental variance that the refractive index of propagation medium changes environmental variance in 11 measurements of environment measurement module and the collection aligning diffracted beam travel path such as temperature, pressure, humidity etc.The travel path of aiming at diffracted beam mainly comprises two parts: the diffracted beam of image-forming module 2 inside is propagated, and propagation medium is mainly the manufacturing material of element in air and the image-forming module, as silicate etc.; The propagation medium that diffracted beam between image-forming module 2 and the alignment mark 5 is propagated is air.In accompanying drawing 1, though only show the environmental variance that environment measurement module 11 is measured between image-forming module and the alignment mark, but be interpreted as the environmental variance that environment measurement module 11 both can have been measured image-forming module inside, also can measure the environmental variance between image-forming module and the alignment mark, perhaps the two is all measured.Environmental variance can be understood as temperature, pressure, humidity etc., and all cause the environmental variance that the propagation medium refractive index changes, and also can directly be interpreted as the refractive index of propagation medium.One of them environmental variance can be measured and gather to environment measurement module 11, as only measuring and collecting temperature, also can gather a plurality of environmental variances.These environmental variances can adopt high speed, high-precision sensor or surveying instrument to measure in real time, and the data that collect will be transferred to alignment function and administration module 10, are used for the correction of aligned position solution procedure.

Alignment function and administration module 10 at first utilize the light intensity data of each passage and the position data of work stage 7 to carry out match, determine phase place or a series of crest location of the diffraction light signals at different levels of each sub-gratings.The corresponding registration signal of the light intensity data of each passage is determined the phase place of registration signal, and then can be determined a series of crest location.Here, the work stage position data is that each channel alignment signal shares.Secondly, the environmental variance that alignment function and administration module 10 utilize environment measurement module 11 to transmit is revised phase place or a series of crest value that each channel alignment signal (the diffraction light signals at different levels of each sub-gratings) match obtains.At last, alignment function and administration module 10 utilize phase place or a series of crest location of revised each channel alignment signal (the diffraction light signals at different levels of each sub-gratings), determine coarse alignment position and the fine alignment position of mark.

The match of light intensity data and work stage position data in alignment function and the administration module 10, determine principle and the method for coarse alignment position and fine alignment position, and each functional module more detailed description of the present invention, at existing patent CN200510030807.0, CN200810033263.7, CN200810035115.9, CN200810040234.3, CN200910052799.8, CN200910047030.7, CN200910194853.2,200910055927.4, US6297876B1, CN03164858.4, CN03164859.2, CN200710045495.X, CN200710044153.6, CN200710044152.1 and document " the many grating markers alignment system that is used for lithographic equipment " (micro-nano electronic technology, 2009,46 (8): 494-497) provide in detail in the grade, here be not further described, but introduce as known technology.

In the present invention, utilize the phase place of environmental variance correction registration signal or the method for peak value can adopt environmental variance-peak mathematical model method or environmental variance-peak table method.In the content below, the embodiment of these two kinds of methods will be provided.But the present invention is not limited to this two kinds of methods, as adopting data-driven methods such as neural network, fuzzy prediction, all can realize utilizing phase place or the peak value of environmental variance correction registration signal.

First embodiment:

One embodiment of the present of invention have provided the method for a series of peak values (for the correction of registration signal phase place, method is identical, because phase place finally can be exchanged into peak value) that utilize environmental variance-peak mathematical model correction registration signal.This method is at first set up the position skew of registration signal peak value and the mathematical model between the environmental variance, utilize the environmental variance of actual measurement to be input in the model then, calculate the peak side-play amount that obtains each channel alignment signal, utilize the peak offset correction peak separately of passage separately then.

The calculating of the peak side-play amount of each channel alignment signal as shown in Figure 2, concrete computing formula is:

$\left\{\begin{array}{c}\mathrm{\Δ\φ}=f(\mathrm{\λ},L,P,T,...,h,P_0,T_0,...,h_0)\\ {\mathrm{\ΔX}}_i=S_i\mathrm{\Δ\φ}\\ X_{\mathrm{peak},i}^{\′}=X_{\mathrm{peak},i}+{\mathrm{\ΔX}}_i\end{array}\right.$ Formula one

In the formula, f () is phase shift function, and Δ φ is phase deviation, and λ is for aiming at illumination wavelengths, and L is for aiming at diffracted beam propagates light path difference, P, T ..., h be pressure, temperature ..., each environmental variance measured value such as humidity, P ₀, T ₀..., h ₀Reference value for working environment.S _iBe the cycle of i channel alignment signal, Δ X _iBe the position deviation of this signal peak, X _{Peak, i}A series of peaks of the i channel alignment signal that obtains for match, X ' _{Peak, i}Peak for revised i channel alignment signal.The reference value of working environment can be the working environment of lithographic equipment alignment system design, is that 1 standard atmospheric pressure, temperature are 293K, relative humidity 45%RH etc. as pressure.Function f () has characterized under specific illumination wavelengths and optical path difference, the relation between environmental variance and the phase deviation, and finally be converted to the peak side-play amount of each channel alignment signal, in order to revise a series of peak X of respective channel _{Peak, i}But concrete approximating method referenced patent CN200510030577.8, CN200510030807.0 and document " the many grating markers alignment system that is used for lithographic equipment " (micro-nano electronic technology, 2009,46 (8): 494-497) etc.

After obtaining a series of peaks of corrected each channel alignment signal, recycling formerly patent CN200810033263.7, CN200710045495.X, CN200710044153.6, CN200710044152.1, CN200810035115.9, CN200810040234.3, CN200910052799.8, CN200910047030.7, CN200910194853.2,200910055927.4 provide catch principle and can determine the coarse alignment position, and on the basis of this coarse alignment position, determine the fine alignment position.For example adopting revised 8.0-1 level light wave peak position and revised 8.8-1 level light wave peak position coincide point is the coarse alignment position; Revised 8.0-3 level photopeak value position near the coarse alignment position is the fine alignment position.

To the end of scan time, environment measurement module 11 all can collect a series of value to each environmental variance, as temperature T from the alignment scanning zero-time ₁, T ₂..., T _nAt this moment, can adopt T ₁To T _nBetween mean value substitution formula one in, constantly value is (as T in the middle of also can adopting _N/2), perhaps adopt other method.

Phase shift function f () can draw by experiment, also can derive by optical principle, and perhaps the two is in conjunction with drawing.Described the two combination namely at first utilizes optical principle to draw basic model, by experimental data basic model is revised then.In one embodiment, adopt Grice pause-Dell's (being Gladstone-Dale) approximate formula determine that temperature and pressure changes and phase deviation between relation.

$\mathrm{\Δ\φ}=\frac{2\mathrm{\πL}}{\mathrm{\λ}}(1+2.9155*{10}^{-8}(\frac{P}{T}-\frac{P_0}{T_0}))$ Formula two

In the formula, P, T are pressure and temperature environmental parameter variable measured value, P ₀, T ₀Be the pressure and temperature reference value, Δ φ is phase deviation, and λ is for aiming at illumination wavelengths, and L is for aiming at diffracted beam propagates light path difference.

With 16 microns cycle sub-gratings ± 5 grades of interference of light are imaged as example, then the peak side-play amount of this channel alignment signal is:

${\mathrm{\ΔX}}_{8.0-5}=\frac{8}{5}\mathrm{\Δ\φ}$ Formula three

Second embodiment:

An alternative embodiment of the invention has provided the method for a series of peak values that utilize environmental variance-peak offset table correction registration signal.Environmental variance-peak offset table is data or historical data foundation by experiment.For the corresponding different environmental variance-peak offset table of different environmental variances.Utilizing actual measurement environmental variance data, by tabling look-up or interpolation obtains the peak skew of each channel alignment signal.Accompanying drawing 3 has provided the peak offset table of air refraction variation with each channel alignment signal.Peak deviation in the table adopts air refraction to equal 1 for calculating benchmark, and namely the crest location under the current refractive index and air refraction are the deviation between 1 o'clock the crest location.Certainly, also can adopt other refractive index as the benchmark of calculating location deviation.Correction formula is:

$X_{\mathrm{peak},i}^{\′}=X_{\mathrm{peak},i}+\mathrm{\Δ}{\hat{X}}_i$ Formula four

In the formula,

For by tabling look-up or interpolation obtains the peak deviation of the i channel alignment signal of environmental variance variable quantity correspondence, X _{Peak, i}A series of peaks of the i channel alignment signal that obtains for match, X ' _{Peak, i}Peak for revised i channel alignment signal.About X _{Peak, i}Match, revise that coarse alignment position and finding the solution of fine alignment position can be with reference to the embodiment of the invention one behind the peak value.

Described in this instructions is several preferred embodiment of the present invention, and above embodiment is only in order to illustrate technical scheme of the present invention but not limitation of the present invention.All those skilled in the art all should be within the scope of the present invention under this invention's idea by the available technical scheme of logical analysis, reasoning, or a limited experiment.

Claims (14)

1. alignment system that is used for lithographic equipment comprises:

Light source and the lighting module of aiming at illuminating bundle are provided; Alignment mark is carried out the image-forming module of imaging; With reference to grating; Gather and see through with reference to the light intensity signal of grating and the signal acquisition process module of handling; Alignment mark; The work stage of carrying silicon chip; The motion platform; Gather the positional information of the work stage of carrying silicon chip, and negotiate synchronously with alignment function and administration module, planning movement locus, the station acquisition of the motion of controlled motion platform and motion-control module; Alignment function and administration module with the signal that receives signal acquisition process module and station acquisition and motion-control module is characterized in that:

Also comprise the environment measurement module, described environment measurement module is used for measuring and gathering and aim at the residing environmental variance of diffracted beam round, and the environmental variance information that collects is transferred to alignment function and administration module; Described alignment function and administration module utilize light intensity data, work stage position data and environmental variance information to determine aligned position.

2. alignment system according to claim 1 is characterized in that: the environmental variance that described environment measurement module is measured image-forming module inside changes, or the environmental variance of measuring between image-forming module and the alignment mark changes, or the two is all measured.

3. alignment system according to claim 2 is characterized in that: described environmental variance is aimed at one or more in the environmental variance of refractive index of diffracted beam propagation medium for influence.

4. alignment system according to claim 3, it is characterized in that: described environmental variance is temperature, pressure and humidity.

5. according to any one described alignment system among the claim 1-4, it is characterized in that: described alignment function and administration module utilize the light intensity data of each passage and the work stage position data that shares, through data fitting, determine a series of peak values of each channel alignment signal.

6. alignment system according to claim 5, it is characterized in that: described alignment function and administration module utilize a series of peak values of each channel alignment signal of environmental variance information correction.

7. alignment system according to claim 6 is characterized in that: described modification method adopts environmental variance-peak skew mathematical model to revise.

8. alignment system according to claim 7 is characterized in that: described environmental variance-peak skew mathematical model is:

In the formula, f () is phase shift function, and Δ φ is phase deviation, and λ is for aiming at illumination wavelengths, and L is for aiming at diffracted beam propagates light path difference, P, T ..., h be pressure, temperature ..., each environmental variance measured value such as humidity, P ₀, T ₀..., h ₀Reference value for working environment.S _iBe the cycle of i channel alignment signal, Δ X _iBe the position deviation of this signal peak, X _{Peak, i}A series of peaks of the i channel alignment signal that obtains for match, X ' _{Peak, i}Peak for revised i channel alignment signal.

9. alignment system according to claim 8, it is characterized in that: described phase shift function is the Gladstone-Dale approximate formula:

In the formula, Δ φ is phase deviation, and λ is for aiming at illumination wavelengths, and L is for aiming at diffracted beam propagates light path difference, and P, T are the measured value of pressure and temperature, P ₀, T ₀Reference value for pressure and temperature.

10. alignment system according to claim 8 is characterized in that: the mean value of each the environmental variance series of measured values when described each environmental variance measured value is alignment scanning perhaps is constantly measured value in the middle of the alignment scanning.

11. alignment system according to claim 6 is characterized in that: described modification method adopts environmental variance-peak offset table to revise.

12. alignment system according to claim 11 is characterized in that: described environmental variance-peak offset table is data or historical data foundation by experiment.

13. alignment system according to claim 11 is characterized in that: described modification method is by tabling look-up or the method for interpolation is carried out.

14. alignment system according to claim 13 is characterized in that: described modification method is:

In the formula,

For by tabling look-up or interpolation obtains the peak deviation of the i channel alignment signal of environmental variance variable quantity correspondence, X _{Peak, i}A series of peaks of the i channel alignment signal that obtains for match, X ' _{Peak, i}Peak for revised i channel alignment signal.

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